The present invention relates to a bistable contactor comprising at least one coil and an armature which is movable relative to the coil and includes contacts and which together with the contacts for opening or closing a circuit can be moved by means of the coil from a first stable position into a second stable position, and a permanent magnet through which the armature is supported in one of its stable positions relative to the coil.
Such a contactor is e.g. known from DE 197 44 396. In this contactor the contacts are resiliently supported on the armature. For opening and closing a circuit the armature is moved by excitation of the coil from a first stable position in which the contacts are spaced apart from corresponding counter-contacts of the relay, into a second stable position in which the contacts rest on the counter-contacts for closing the circuit. The permanent magnet is secured to the armature and is thus movable relative to the coil. The coil is briefly excited for moving the armature between its two stable positions. In the non-excited state, a magnetic circuit is respectively closed by the permanent magnet in the two stable positions so that the armature is respectively held in one of the two stable positions. However, the inertia of the armature is increased due to the permanent magnet. Contact problems may in particular arise in the case of vibration-induced loads. The switching speed is also limited thereby.
It is therefore an object of the invention to further develop bistable contactors of the above-mentioned kind in such a manner that higher switching speeds can be achieved and a reliable contact is ensured in the closed state of the circuit at the same time.
Said object is achieved according to the invention by the features that the permanent magnet is stationary relative to the coil and that there is provided a spring element which biases the armature into the other bistable position to be spaced apart from the permanent magnet.
Such a solution is simple and offers the advantage that the permanent magnet need no longer be mounted on the armature. Instead of this, the permanent magnet can e.g. be mounted on a housing to be stationary relative to the coil. The armature can thus be configured with a reduced weight. Thanks to such a lightweight armature the contact reliability can in particular be enhanced in the case of vibration-induced loads. This also permits a simple structure of the contactor. Fewer demands are made on the guide characteristics of the armature.
In a further advantageous development of the invention, the armature may rest on the permanent magnet, preferably the pole shoe thereof, in the one of the two bistable positions. A particularly stable position of the armature can be realized thereby because in contrast to conventional bistable contactors there is no air gap between armature and permanent magnet in the respective stable position.
Moreover, it may turn out to be of advantage when the circuit is closed in the stable position produced by the permanent magnet. An inadvertent opening of the circuit can thereby be avoided with the permanent magnet.
In an advantageous development of the invention there may be provided two coils, with the armature being movable into one of its two stable positions by excitation of a respective coil. As a result, the polarity of the coil need not be reversed for moving the armature between the two stable positions. Instead of this, a respective coil can be used for movement into one of the two positions. The circuit expenditure can thus be reduced.
It may be of advantage when the coils are designed as cylindrical coils which are concentrically arranged relative to one another. The two coils can thereby be arranged in a compact manner.
Moreover, it may turn out to be of advantage when the permanent magnet is arranged inside the one coil or the coils. The contactor can also be made more compact in this way. Moreover, a strong magnetic flux can be produced by the permanent magnets arranged within the coil or one of the coils.
It might also turn out to be of advantage when the spring element is designed as a compression spring. Thanks to such a compression spring the armature can be biased in a reliable and easy manner into one of its two stable positions.